Biomass upgrading requires the feeding of a variety of particulate solid materials such as wood chips, sawdust, yard waste, cuttings, other vegetation; agricultural products and agricultural waste (e.g., corn stover, bagasse, fruit, garbage, silage, etc.); energy crops (e.g. switchgrass, miscanthus); algae and other marine plants; metabolic wastes (e.g., manure, sewage); and cellulosic urban waste etc., to a fluidized bed of catalyst for catalytic fast pyrolysis. Partially upgraded or converted biomass, such as pyrolysis oils, carbohydrates, digestion products or the like, that are often liquids or semi-solids, could also be used in the process, either alone or in combination with solid feeds.
The catalytic fast pyrolysis process (CFP) of biomass requires the conversion of a variety of high molecular weight materials such as lignin, cellulose, and hemi-cellulose, by pyrolysis in the presence of a catalyst, preferably an acidic, micro-porous catalyst, usually a zeolite. The zeolite is active for the upgrading of the primary pyrolysis products of biomass decomposition, and converts them to aromatics, olefins, CO/CO2, char, coke, water, and other useful materials.
For the catalytic fast pyrolysis process (CFP) to be effective, biomass must not be heated above the temperature at which pyrolysis begins, typically about 150-200° C., before it is in the vicinity of the catalyst to maximize the interaction of the primary pyrolysis products with the catalyst for conversion to aromatics, olefins and other useful materials. At the same time, when the biomass is heated, it must be heated very rapidly, at heating rates as much as 500° C./sec, to minimize formation of char and maximize the production of useful materials. Thus, a problem in the fast pyrolysis and catalytic fast pyrolysis of biomass is how to introduce the biomass feed into the pyrolysis reactor, keeping it from heating prematurely in the feed line where char can form and yet heating it very rapidly once it enters the reaction zone.
Screw auger feed devices have been used to feed the biomass to fluidized bed reactors, but the linear flow rate of the biomass is relatively slow in the feed auger, so the biomass can be heated as it approaches the hot catalyst bed, resulting in char formation and low yields of aromatics and olefins. Premature partial pyrolysis of the biomass also releases oily intermediates that can clog the movement of the auger. Scale up of the auger feed system is problematic as well since an auger that extends into the center of a large reactor would necessarily become quite hot or would require cooling that wastes heat and cools the reactor bed. The present invention overcomes the problems involved in feeding biomass into a hot, fast pyrolysis or hot, catalytic fast pyrolysis reactor by use of a gas jet to feed the biomass into the fluid bed.
In U.S. Pat. No. 6,105,275, a continuous rotary vacuum retort apparatus and its use are described. The patent mentions the use of elastomeric pinch valves used to create an airlock in a vacuum retort but not operation under elevated pressures or as feed system for a catalyzed fluid bed. In EP 0075899, a process for transferring solids is described in which a gas is used as a barrier for metering of solids between two pressure controlled vessels. In EP 0820419 B1, an air lock for pneumatic conveyance and separation of solids from the conveying air is described that employs a rotary airlock for removing solids from conveying airstream. In WO 1996018564 B1, a vertical-shaft airlock is described that uses rotating mechanical seals. In WO 2013095163 A1, a continuous pyrolysis apparatus is described wherein pyrolysis occurs on an auger with material admitted and expelled by use of airlocks. No airlock structure specified beyond ‘valves’. In US 20130019492, a system for the continuous treatment of solids at non-atmospheric pressure is described using a semi-batch airlock that is loaded with enough material to continuously supply a process prior to being reloaded as in a typical lock-hopper system.
Asadullah et al., in “Biomass Gasification to Hydrogen and Syngas at Low Temperature: Novel Catalytic System Using Fluidized-Bed Reactor,” J. Catal. 208, 255-259 (2002), described an experimental combustion system in which cellulose was continuously transported into a fluidized catalyst bed through a 5 mm outlet in a feed hopper by the flow of N2 gas through an inner tube of 5 mm inner diameter into a concentric tube of 18 mm inner diameter containing a catalyst bed containing a Rh/CeO2/SiO2 catalyst. The cellulose was converted to hydrogen and CO.
Eastham et al. in U.S. Pat. No. 5,968,460 and U.S. Pat. No. 5,175,943 describe methods of continuously adding solids to a combustion process conducted in a fluidized bed from a standpipe having an angle that has a bend to hold back the solids. The standpipe contains gas inlets to maintain the pressure slightly above that in the fluidized bed. The gases added to the standpipe can be used to fluidize the solids in the standpipe and lessen the binding of particles.
Medoff in US 2012/0094355 describes a noncatalytic process in which pressurized gases can be added to a biomass-derived feedstock stream to propel the feedstock into a pyrolysis chamber to produce sugars or amino acids.
Jones, in U.S. Pat. No. 4,474,119 discloses a fluidized bed combustion furnace in which coarse limestone is added through a nozzle into the fluidized bed and solid fines are added along with the fluidization fluid. The fine feed solids can be added tangentially.
Rozainee et al., in “Effect of Feeding Methods on the Rice Husk Ash Quality in a Fluidised Bed Combustor,” Emirates J. Eng. Res., 15, 1-12 (2010), reported the results of a study in which rice husks are fed by gas injection into a fluidized bed combustion chamber from an inlet inclined at a 45° angle. The ash produced in the combustion when feed entered the reaction chamber from a tangentially disposed inlet was reported to have smaller particle size and lower carbon content than ash produced with radial feed.
North et al. (Nova Pangea Technologies) in US Patent Appl 20110100359 describes a 5-step process that includes entraining biomass solids in a flow of superheated steam in a steam loop to cause the cells to explode prior to introduction of the biomass in a hydrolysis reactor and condensation of the hydrolyzed sugar-containing materials. Zielinski et al. in U.S. Pat. No. 4,309,948 describe delivery of an entrained stream of carbonaceous solid particles to a catalyst bed through a mushroom-shaped cap. Wachter in U.S. Pat. No. 5,688,472 describes using a downward flow of gas through an annulus to fluidize a reactor bed. Klajay et al. in US 2012/0251959 disclose a fluidized bed fuel feed system that introduces the solid fuel along a channel in the wall into a grid section to increase the time of the heatup of the fuel to dry the fuel, i.e., reduce the rate of heating, before it enters the turbulent fluid bed. Bartek in U.S. Pat. No. 8,523,496 describes a process for feeding biomass to a reactor for conversion to oxygenated hydrocarbons that utilizes a spool piece adapted to convey solids from a lower pressure to a higher pressure; however, other than increasing pressure, no steps are taken to control injection conditions or reduce preheating of the biomass.
Thus a need exists for a process and apparatus for feeding biomass to a fluid bed or similar reactor that minimizes premature heating of the biomass and mixes it rapidly with the materials in the reactor.